Many things have combined to make very high-frequency RF gear much more common, cheaper, and better performing. Case in point: [dereksgc] is tearing apart a 20 GHz low-noise block (LNB). An LNB is a downconverter, and this one is used for some Irish satellite TV services.
The scale of everything matters when your wavelength is only 15 mm. The PCB is small and neatly laid out. There are two waveguides printed on the board, each feeding essentially identical parts of the PCB. Printed filters use little patterns on the board that have particular inductance and capacitance — no need for any components. Try doing that at 2 MHz!
The LNB is a single-band unit, so it only needs to worry about the two polarizations. However, [dereksgc] shows that some have multiple bands, which makes everything more complex. He also mentions that this LNB doesn’t use a PLL, and he’d like to find a replacement at this frequency that is a bit more modern.
After the teardown, it is time to test the device to see how it works. If you want to experiment at this frequency, you need special techniques. For example, we’ve seen people try to push solderless breadboards this high (spoiler: it isn’t easy). Maybe that’s why many people settle for modifying existing LNBs like this one.
Learn the term “mixer”
It is a little unclear to me what you mean.
Why all the holes in the conductors?
The “holes” are vias. They connect a trace on one side to a trace on the other side.
The traces with vias are on this board (mostly) ground traces. The vias connect the ground traces with the ground plane on the bottom side.
Tying the traces to the ground plane helps to maintain a constant impedance between the ground traces and the signal traces.
It’s been a while (6 years) since I worked with satellite equipment.
This reminded me of:
Triax (RIP) made a LNB PCB with wide band tuner FPGA, and POE Ethernet.
They joked “Why is the PCB so expensive when it’s mostly made of holes?”